Harmonic suppression and heat loss evaluation method and system for power distribution network

Abstract

The invention discloses a power distribution network harmonic suppression and heat loss evaluation method and system, and relates to the technical field of electric energy quality optimization and heat loss evaluation, and the method comprises the steps: collecting a power distribution network signal, extracting harmonic features, and calculating the harmonic contribution degree of each load based on a harmonic power flow; cable additional heat loss caused by harmonic current is calculated, and cable temperature prediction is carried out based on a transient heat conduction equation; and dynamically adjusting parameters of the harmonic compensation device according to harmonic treatment and heat loss evaluation results, and optimizing load scheduling. According to the method, more accurate harmonic source identification and harmonic power flow calculation are provided, and the harmonic treatment accuracy is improved; in cable heat loss evaluation, eddy current loss modeling, heat conduction analysis and dynamic temperature prediction are introduced, so that the operation safety of the cable is enhanced; dynamic harmonic suppression optimization and load scheduling are combined, a closed-loop regulation mechanism is formed, the electric energy quality is improved, and meanwhile, the cable overheating risk is effectively avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of power quality optimization and heat loss assessment, and specifically to a method and system for harmonic governance and heat loss assessment in a distribution network. Background Technique

[0002] With the rapid development of modern power systems, power quality problems in distribution networks have become increasingly prominent; due to the widespread application of large-scale power electronic devices, frequency converters, and nonlinear loads (such as electric vehicle charging stations, data centers, etc.), the harmonic pollution problem in the power grid has become even more serious; harmonics not only cause waveform distortion of grid voltage and current, affecting the normal operation of equipment, but also lead to an increase in reactive power loss, reducing the energy transmission efficiency of the power grid; in addition, harmonic currents in cables can cause additional heat loss, resulting in abnormal cable temperature rise, accelerating the aging of insulating materials, shortening the service life of cables, and even causing equipment overheating failures; for harmonic governance and heat loss assessment, currently mainly passive filters, active power filters (APF), static var compensators (SVG), etc. are used for governance, and at the same time, thermal sensors are used to monitor cable temperature; however, traditional methods still have many limitations in the accuracy, self-adaptability, and overall optimization control of harmonic governance and heat loss assessment, and there is an urgent need for more intelligent and accurate governance strategies to improve the safety and reliability of power grid operation.

[0003] The current harmonic governance technology mainly relies on the combined compensation strategy of passive filters and active power filters. However, passive filters can only compensate for fixed-frequency harmonics and are difficult to adapt to the dynamic changes of grid loads. Although active power filters have strong harmonic compensation capabilities, they have high energy consumption and still have insufficient compensation when dealing with complex multiple harmonic coupling problems; in addition, existing harmonic power flow analysis methods usually use static models and do not fully consider the dynamic impact of different loads on the harmonic propagation path, resulting in large errors in harmonic source identification and contribution calculation and unable to achieve precise harmonic governance optimization; in addition, most traditional cable heat loss assessment methods are based on fixed-point temperature measurement, relying on limited sensor deployment for temperature monitoring, and do not fully consider the non-uniform heat loss distribution caused by harmonics, resulting in large errors in temperature rise prediction; existing heat conduction models also do not fully combine harmonic loss characteristics and cannot accurately quantify the impact of harmonics on cable life; in addition, traditional harmonic governance and load dispatching strategies usually operate separately and lack a systematic collaborative optimization control method, making it difficult to simultaneously consider power grid harmonic governance and heat loss control; therefore, there is an urgent need for a comprehensive solution that can accurately extract harmonic characteristics, establish a harmonic power flow analysis model, accurately predict cable heat loss, and dynamically adjust harmonic compensation and load dispatching through intelligent optimization strategies to improve the overall stability and operation efficiency of the power grid. Summary of the Invention

[0004] In view of the above-mentioned problems, the present invention is proposed.

[0005] Therefore, the technical problem solved by the present invention is: the compensation effect of the existing harmonic control method is greatly affected by the dynamic changes of the load and is difficult to optimize in real time. The harmonic power flow analysis accuracy is insufficient, resulting in large errors in harmonic source identification. The means for evaluating cable heat loss are limited, making it difficult to accurately predict temperature rise and its impact on cable life. The problem also involves how to dynamically adjust the parameters of the harmonic compensation device based on the harmonic control and heat loss evaluation results, and optimize load scheduling to reduce the risk of cable temperature rise.

[0006] To solve the above technical problems, the present invention provides the following technical solutions: a method for harmonic control and heat loss assessment of a distribution network, comprising collecting distribution network signals, extracting harmonic characteristics, and calculating the harmonic contribution of each load based on harmonic power flow; calculating the additional heat loss of the cable caused by harmonic current, and predicting the cable temperature based on the transient heat conduction equation; and dynamically adjusting the parameters of the harmonic compensation device according to the results of harmonic control and heat loss assessment to optimize load scheduling.

[0007] As a preferred solution of the method for harmonic control and heat loss assessment of distribution network described in the present invention, the extraction of harmonic features includes deploying harmonic monitoring equipment at the distribution network nodes, collecting three-phase voltage and current signals in real time, and the sampling frequency satisfies the Nyquist sampling theorem to capture each harmonic component; using Fourier transform to perform spectrum analysis on the collected signal to obtain the amplitude and phase information of each harmonic, and combining short-time Fourier transform to perform time-frequency domain analysis, extract harmonic change characteristics, identify harmonic sources and quantify harmonic intensity.

[0008] As a preferred solution of the method for harmonic control and heat loss assessment of distribution network described in the present invention, wherein: the calculation of the harmonic contribution of each load includes measuring the voltage and current at each monitoring point based on the harmonic current characteristics of each load in the distribution network, extracting each harmonic component, establishing a harmonic current injection model for each load, and calculating the harmonic current injection amount of each load; establishing a grid impedance model at different harmonic frequencies based on the frequency dependence characteristics of the line impedance, combining the harmonic current injection model of each load, calculating the harmonic power flow at different frequencies, and solving the harmonic voltage of each node based on an iterative method, and calculating the harmonic voltage distortion contribution of each load at each harmonic frequency; based on the harmonic current injection amount of each load and the harmonic voltage distortion of each node, calculating the contribution of each load to the total harmonic distortion rate of the distribution network, constructing a load harmonic contribution matrix based on the relative influence relationship of different loads, and quantifying the influence of each load on the overall power quality.

[0009] As a preferred solution of the method for harmonic governance and heat loss assessment of the distribution network described in the present invention, wherein: calculating the additional heat loss of the cable caused by harmonic current includes performing an electromagnetic field effect analysis, calculating the additional loss caused by the eddy current effect based on the non-uniform distribution of harmonic current in the conductor, associating the additional loss proportionally with the square of the harmonic frequency to distinguish the additional loss from the fundamental wave loss; establishing a heat transfer model inside the cable based on the heat conduction characteristics of the cable, calculating the heat transfer rate between different layer structures of the cable according to the thermal resistance characteristics of the conductor and the insulation layer, taking the heat generated by harmonic loss as the heat source term, and deducing the temperature rise situation of the cable in the actual operating environment to quantify the impact of harmonics on the heat loss of the cable.

[0010] As a preferred solution of the method for harmonic governance and heat loss assessment of the distribution network described in the present invention, wherein: predicting the cable temperature based on the transient heat conduction equation includes using the transient heat conduction equation to establish a cable temperature field model and calculating the temperature rise trend of the cable over time; monitoring the cable temperature through fiber optic temperature sensors and infrared thermal imaging devices, and combining time series to predict the cable temperature to identify overheating risks in advance and optimize the operation management of the cable.

[0011] As a preferred solution of the method for harmonic governance and heat loss assessment of the distribution network described in the present invention, wherein: dynamically adjusting the parameters of the harmonic compensation device includes analyzing the amplitude and phase of each harmonic current according to the measured harmonic frequency components and calculating the total harmonic distortion rate of the current distribution network. If it exceeds the set target value, further analyze the contribution degree of each load to harmonics to determine the main harmonic source; select the corresponding compensation strategy according to the characteristics of the main harmonic source, adjust the output frequency band of the active filter according to the grid impedance characteristics of each harmonic frequency band so that the output frequency band covers the main harmonic components, and at the same time adjust the compensation parameters of the passive filter to optimize filtering; after adjusting the parameters of the compensation device, re-obtain the harmonic measurement data of the distribution network and calculate the total harmonic distortion rate after adjustment. If the target value is still not reached, iteratively optimize and adjust the operating state of the compensation device until the harmonic level drops within the set range or reaches the adjustment limit of the compensation device; during the adjustment process of the harmonic compensation device, detect the change in cable temperature. If the temperature rise exceeds the safety threshold, limit the operating range of the compensation device.

[0012] As a preferred solution of the method for harmonic governance and heat loss assessment of the distribution network described in the present invention, wherein: optimizing the load scheduling includes determining the current load operating state according to the cable temperature prediction result and calculating the influence range of high-order harmonics on the cable temperature rise; comparing the predicted value of the cable temperature rise with the safe operating threshold. In the case of exceeding the safe operating threshold, use discrete-time dynamic programming to optimize the load scheduling and reduce the instantaneous peak load.

[0013] Another object of the present invention is to provide a distribution network harmonic governance and heat loss assessment system, which can calculate the additional heat loss of the cable caused by harmonic current, predict the cable temperature based on the transient heat conduction equation, and solve the problem of large errors in harmonic source identification in the current harmonic governance technology.

[0014] As a preferred embodiment of the distribution network harmonic governance and heat loss assessment system described in the present invention, it includes a harmonic analysis module, a cable temperature prediction module, and a governance optimization module; the harmonic analysis module is used to collect distribution network signals, extract harmonic characteristics, and calculate the harmonic contribution degree of each load based on the harmonic power flow; the cable temperature prediction module is used to calculate the additional heat loss of the cable caused by harmonic current and predict the cable temperature based on the transient heat conduction equation; the governance optimization module is used to dynamically adjust the parameters of the harmonic compensation device and optimize the load scheduling according to the harmonic governance and heat loss assessment results.

[0015] A computer device includes a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps of the distribution network harmonic governance and heat loss assessment method.

[0016] A computer-readable storage medium stores a computer program thereon. When the computer program is executed by a processor, it implements the steps of the distribution network harmonic governance and heat loss assessment method.

[0017] The beneficial effects of the present invention: The distribution network harmonic governance and heat loss assessment method provided by the present invention provides more accurate harmonic source identification and harmonic power flow calculation, improves the accuracy of harmonic governance, and provides data support for subsequent optimization; in the cable heat loss assessment, eddy current loss modeling, heat conduction analysis, and dynamic temperature prediction are introduced, improving the early warning ability for cable overheating and enhancing the safety of cable operation; combining dynamic harmonic governance optimization and load scheduling forms a closed-loop adjustment mechanism, improving the power quality, effectively avoiding the risk of cable overheating, and ensuring the long-term stable operation of the distribution network. The present invention has achieved better results in terms of accuracy, safety, and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0019] Figure 1 It is the overall flowchart of the distribution network harmonic governance and heat loss assessment method provided by the first embodiment of the present invention.

[0020] Figure 2 This is the overall flowchart of the distribution network harmonic governance and heat loss assessment system provided by the third embodiment of the present invention. Specific implementation manners

[0021] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following will describe the specific implementation manners of the present invention in detail with reference to the accompanying drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0022] Embodiment 1, referring to Figure 1 This is an embodiment of the present invention, which provides a method for distribution network harmonic governance and heat loss assessment, including:

[0023] S1: Collect distribution network signals, extract harmonic features, and calculate the harmonic contribution degree of each load based on the harmonic power flow.

[0024] Furthermore, extracting harmonic features includes deploying harmonic monitoring devices at distribution network nodes to collect three-phase voltage and current signals in real time. The sampling frequency satisfies the Nyquist sampling theorem to capture each harmonic component; performing spectral analysis on the collected signals using Fourier transform to obtain the amplitude and phase information of each harmonic, and combining short-time Fourier transform for time-frequency domain analysis to extract harmonic change features, identify harmonic sources, and quantify harmonic intensity.

[0025] It should be noted that calculating the harmonic contribution degree of each load includes, based on the harmonic current characteristics of each load in the distribution network, measuring the voltage and current at each monitoring point respectively, extracting each harmonic component, establishing a harmonic current injection model for each load, and calculating the harmonic current injection amount of each load; based on the frequency-dependent characteristics of the line impedance, establishing a power grid impedance model at different harmonic frequencies, combining the harmonic current injection models of each load, calculating the harmonic power flow at different frequencies, and solving the harmonic voltage at each node based on an iterative method to calculate the harmonic voltage distortion contribution amount of each load at each harmonic frequency; based on the harmonic current injection amount of each load and the harmonic voltage distortion situation at each node, calculating the contribution degree of each load to the total harmonic distortion rate of the distribution network, and constructing a load harmonic contribution degree matrix according to the relative influence relationship of different loads to quantify the influence of each load on the overall power quality. A preferred scheme for calculating the contribution degree of each load to the total harmonic distortion rate of the distribution network includes using an iterative algorithm to solve the contribution degree of each load to the total harmonic distortion rate THD of the whole network, expressed as:

[0026]

[0027] Where Ch is the harmonic contribution degree for the h-th harmonic of the load, representing the relative contribution degree of the load to the total harmonic distortion (THD) of the system, with a value range of [0, 1]; I h is the amplitude of the harmonic current of the h-th harmonic of the load, in amperes (A), used to measure the current magnitude of the load at a specific harmonic frequency; Z h is the equivalent harmonic impedance of the h-th harmonic of the load, in ohms (Ω), used to represent the electrical impedance characteristics of the load at the harmonic frequency; H is the total number of harmonics, that is, the maximum index value of different harmonic orders considered in the calculation, usually depending on the analysis accuracy requirements. For example, H = 50 means calculating up to the 50th harmonic; d i is the spatial propagation distance from the load at position i to the harmonic monitoring point, in meters (m), used to characterize the geographical relationship between the harmonic source and the monitoring point; N is the total number of all loads in the system. Existing harmonic power flow analysis usually calculates the contribution degree only based on the current magnitude. Our invention incorporates the influence of the load position into the calculation and optimizes the accuracy of harmonic source identification.

[0028] It should also be noted that by deploying harmonic monitoring equipment at the nodes of the distribution network, real-time collection of three-phase voltage and current signals is carried out, and Fourier transform is used to perform spectral analysis on the signals to obtain the amplitude and phase information of each harmonic. Combining short-time Fourier transform for time-frequency domain analysis to extract harmonic change characteristics to achieve accurate identification of power grid harmonics; by measuring the voltage and current at each monitoring point respectively, extracting each harmonic component, and combining the harmonic current characteristics of each load in the distribution network, a harmonic current injection model is established; based on the frequency-dependent characteristics of the line impedance, a power grid impedance model at different harmonic frequencies is constructed, and combined with the harmonic current injection model, the harmonic power flow at different frequencies is calculated, and the harmonic voltage of each node is solved using an iterative method, and finally the harmonic voltage distortion contribution amount of each load at each harmonic frequency is calculated; compared with the traditional static or empirical method for calculating the harmonic contribution degree, our invention can effectively improve the accuracy of harmonic source identification through accurate frequency domain and time-frequency domain analysis, combined with the power grid impedance characteristics and harmonic power flow solution, providing a more accurate analysis basis for subsequent harmonic governance.

[0029] S2: Calculate the additional heat loss of the cable caused by harmonic current and predict the cable temperature based on the transient heat conduction equation.

[0030] Further, calculating the additional cable heat loss caused by harmonic current includes performing an electromagnetic field effect analysis. Based on the non-uniform distribution of harmonic current in the conductor, the additional loss caused by the eddy current effect is calculated, and the additional loss is proportionally related to the square of the harmonic frequency to distinguish the additional loss from the fundamental wave loss. A preferred solution for calculating the additional cable heat loss caused by harmonic current includes calculating the losses caused by each harmonic current and calculating the iron loss and eddy current loss caused by harmonics based on the Steinmetz empirical formula to establish a mathematical model of the additional harmonic heat loss of the cable, expressed as:

[0031]

[0032] R h =R dc (1+βh 2 )

[0033] Where, Q h is the total heat loss caused by harmonics, H is the total number of harmonic orders, I h is the current amplitude corresponding to the harmonic order h, R h is the equivalent resistance corresponding to the harmonic order h, γ is the additional loss coefficient related to the harmonic frequency, h is the harmonic order, R dc is the resistance of the cable under DC conditions, β is the harmonic loss correction coefficient of the cable material, which is used to describe the influence of high-frequency harmonics on the skin effect and proximity effect of the conductor. Most of the existing cable loss calculations only consider the fundamental wave loss, while our invention improves the calculation accuracy through the high-order harmonic loss model, quantifies the influence of high-order harmonic frequency on the cable heat loss, and improves the thermal management prediction ability of the cable during long-term operation.

[0034] Based on the heat conduction characteristics of the cable, a heat transfer model inside the cable is established. According to the thermal resistance characteristics of the conductor and the insulation layer, the heat transfer rate between different layer structures of the cable is calculated. The heat generated by the harmonic loss is used as the heat source term to deduce the temperature rise situation of the cable in the actual operating environment and quantify the influence of harmonics on the cable heat loss.

[0035] It should be noted that predicting the cable temperature based on the transient heat conduction equation includes using the transient heat conduction equation to establish a cable temperature field model and calculating the temperature rise trend of the cable over time; monitoring the cable temperature through fiber optic temperature sensors and infrared thermal imaging equipment, and combining time series to predict the cable temperature to identify overheating risks in advance and optimize the cable operation management.

[0036] It should also be noted that by analyzing the electromagnetic field effect, based on the non-uniform distribution of harmonic current in the conductor, the additional loss caused by the eddy current effect is calculated, and the additional loss is proportionally correlated with the square of the harmonic frequency to distinguish it from the fundamental wave loss. Combining with the heat conduction characteristics of the cable, a heat transfer model inside the cable is established. According to the thermal resistance characteristics of the conductor and the insulation layer, the heat transfer rate between different layer structures of the cable is calculated; the heat generated by the harmonic loss is used as the heat source term, and a cable temperature field model is established based on the transient heat conduction equation to calculate the temperature rise trend of the cable over time. Combining with fiber optic temperature sensors and infrared thermal imaging equipment for cable temperature monitoring, and at the same time using time series prediction methods to analyze the future cable temperature change trend; traditional cable heat loss assessments are mostly based on fixed loads and linear heat conduction models, ignoring the influence of higher harmonics. The present invention not only introduces eddy current loss modeling, but also combines harmonic heat source terms and dynamic heat conduction analysis, making cable temperature prediction more accurate, improving the early warning ability for cable overheating risks, and avoiding cable insulation aging or failures caused by overheating.

[0037] S3: Dynamically adjust the parameters of the harmonic compensation device according to the harmonic governance and heat loss assessment results, and optimize the load dispatching.

[0038] Furthermore, dynamically adjusting the parameters of the harmonic compensation device includes analyzing the amplitude and phase of each harmonic current according to the measured harmonic frequency components, and calculating the total harmonic distortion rate of the current distribution network. If it exceeds the set target value, further analyze the contribution of each load to the harmonics to determine the main harmonic source; according to the characteristics of the main harmonic source, select the corresponding compensation strategy, adjust the output frequency band of the active filter according to the grid impedance characteristics of each harmonic frequency band, so that the output frequency band covers the main harmonic components, and at the same time adjust the compensation parameters of the passive filter to optimize the filtering; after adjusting the parameters of the compensation device, re-obtain the harmonic measurement data of the distribution network, and calculate the total harmonic distortion rate after adjustment. If it still does not reach the target value, iteratively optimize and adjust the operating state of the compensation device until the harmonic level drops to the set range or reaches the adjustment limit of the compensation device; a preferred iterative optimization scheme includes adopting a control strategy based on an optimization algorithm, enabling the harmonic compensation device to dynamically adjust the compensation ability according to the load change, and the optimization algorithm is expressed as:

[0039]

[0040] where P opt is the optimal compensation power, P is the compensation adjustment parameter, I h is the harmonic current amplitude at harmonic frequency h, Z h is the equivalent impedance at harmonic frequency h, C h is the contribution of the h-th harmonic of the load, H is the total number of harmonics, ω hTo dynamically optimize the weight, the compensation power parameter P is minimized and optimized. In the control strategy of the compensation device (such as the active power filter APF) of the present invention, a dynamic weight optimization factor based on real-time harmonic measurement is introduced to ensure that the filter can preferentially process the harmonics with the greatest impact. The existing harmonic compensation control strategies usually perform fixed-parameter compensation, while the invention of our side automatically adjusts the compensation power according to the real-time measured harmonic intensity to improve the treatment effect; it breaks through the static parameter configuration method of traditional filters and realizes dynamic adaptive harmonic compensation.

[0041] During the adjustment process of the harmonic compensation device, the change in the cable temperature is detected. If the temperature rise exceeds the safety threshold, the operating range of the compensation device is restricted.

[0042] It should be noted that optimizing the load scheduling includes determining the current load operating state based on the cable temperature prediction result and calculating the influence range of the high-order harmonics on the cable temperature rise; comparing the predicted value of the cable temperature rise with the safe operating threshold. In the case of exceeding the safe operating threshold, discrete-time dynamic programming is used to optimize the load scheduling to reduce the instantaneous peak load.

[0043] It should also be noted that by measuring the harmonic frequency components of the current distribution network, analyzing the amplitude and phase of each harmonic current, and calculating the total harmonic distortion rate of the current distribution network, if it exceeds the set target value, the contribution degree of each load to the harmonics is further analyzed to identify the main harmonic sources, and corresponding compensation strategies are selected according to the characteristics of the main harmonic sources; according to the grid impedance characteristics of each harmonic frequency band, the output frequency band of the active power filter is adjusted to cover the main harmonic components, and at the same time, the compensation parameters of the passive power filter are adjusted to optimize the filtering. After adjusting the parameters of the compensation device, the harmonic measurement data of the distribution network are re-obtained, and the adjusted total harmonic distortion rate is calculated. If the target value is still not reached, the operating state of the compensation device is iteratively optimized and adjusted until the harmonic level drops to the set range or reaches the adjustment limit of the compensation device; at the same time, during the adjustment process of the harmonic compensation device, the change in the cable temperature is detected. If the temperature rise exceeds the safety threshold, the operating range of the compensation device is restricted; by dynamically adjusting the parameters of the harmonic compensation device, the harmonic treatment strategy can be adaptively adjusted to ensure that the power quality meets the standards and avoid additional energy consumption of the equipment or unnecessary filtering losses caused by over-compensation; in addition, through the feedback control of the cable temperature monitoring, the compensation strategy can be further optimized to ensure harmonic treatment while avoiding excessive cable temperature rise; compared with the traditional static harmonic compensation strategy, this method introduces a dynamic harmonic treatment optimization mechanism and combines cable temperature feedback to realize the coordinated optimization of the compensation device and the load scheduling, making the power grid operation more stable, the power quality more reliable, reducing the failure risk caused by cable overheating, and improving the overall operation efficiency of the distribution network.

[0044] Embodiment 2 is an embodiment of the present invention, which provides a method for harmonic governance and thermal loss assessment of a distribution network. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments.

[0045] First, a typical industrial area was selected as the test area in a certain 35 kV distribution network; there are multiple non-linear loads in this area, including equipment such as frequency converters, electric arc furnaces, and rectifiers. These devices usually generate a large amount of harmonics, affecting power quality and increasing the thermal loss of the cable; the main objective of this experiment is to collect the harmonic signals of the distribution network, analyze the harmonic contribution of each load, and calculate the impact of harmonics on the cable temperature rise. At the same time, the grid harmonic level and cable temperature rise are reduced by optimizing the compensation strategy; high-precision harmonic monitoring equipment (PMU) is installed at multiple nodes of the distribution network to collect three-phase voltage and current data in real time. The sampling frequency is 10 kHz, which meets the Nyquist sampling theorem; the collected data is used to extract the amplitude and phase of each harmonic through Fourier transform (FFT), and the time-varying characteristics of harmonics are analyzed in combination with short-time Fourier transform (STFT); after obtaining the harmonic current characteristics, the harmonic injection amounts of different loads are compared, and the harmonic power flow at each harmonic frequency is calculated in combination with the grid impedance model; subsequently, based on the iterative calculation method, the harmonic voltage distortion contribution of each load at different harmonic frequencies is solved to form a load harmonic contribution matrix, and finally the main harmonic sources and their influence degrees are determined; for the main power supply cable of the industrial park (model YJV-3×240mm 2 ), its harmonic current component is measured, and the additional thermal loss caused by high-frequency harmonics is calculated; the Steinmetz empirical formula is used in the experiment to analyze the harmonic iron loss and eddy current loss, and the cable temperature rise trend is calculated based on the transient heat conduction equation; in order to improve the accuracy of temperature prediction, an optical fiber temperature sensor is installed on the cable surface to record the temperature change in real time, and temperature prediction is carried out in combination with the time series model to identify possible overheating risks in advance; during the adjustment of the compensation strategy, first detect the current total harmonic distortion rate (THD). If the THD exceeds 5% (the national standard GB / T14549-93 stipulates that the THD of the power supply system should be lower than 5%), then start the active power filter (APF) to compensate the high-order harmonics in real time, and dynamically adjust the compensation power according to the optimization algorithm; in addition, in order to avoid cable overheating, after the compensation strategy is adjusted, detect the change in cable temperature rise. If the temperature exceeds 75 °C (the safe operating temperature of the cable insulation), then optimize the load scheduling strategy, adjust the operation time of high-power non-linear loads, and reduce the instantaneous harmonic load; refer to Table 1 for data recording and analysis.

[0046] Table 1 Experimental data record table

[0047]

[0048] As can be seen from the table data, the harmonic contribution degrees of loads L1 and L4 are relatively high, reaching 30.5% and 25.3% respectively, which means that these two loads are the main harmonic sources; by implementing the method of the present invention, after optimizing the compensation scheme, the total harmonic distortion rate (THD) of the distribution network is reduced from 7.2% to 3.5%, effectively meeting the national standard requirements; this result shows that the calculation method of load contribution degree based on harmonic power flow can accurately identify high-harmonic loads and perform targeted compensation, improving the accuracy of harmonic governance; the data shows that before harmonic governance, the temperatures of the cables are generally high. For example, the final temperatures of the cables corresponding to loads L1 and L4 reach 62.1°C and 60.2°C respectively, showing a large increase compared to the initial temperature; after optimization, by reducing the influence of high-order harmonics on the heat loss of the cables, the final cable temperature drops to 49.3°C, reducing the overheating risk caused by harmonics; this experiment verifies that the high-order harmonic loss calculation model of the present invention can accurately predict the cable temperature rise trend and effectively reduce the heat loss of the cables by optimizing the harmonic compensation strategy; the calculation method based on load harmonic contribution degree: by introducing the frequency-dependent characteristics of line impedance and combining harmonic power flow analysis, a more accurate harmonic contribution degree matrix is established, improving the identification accuracy of harmonic sources; the harmonic compensation strategy based on the optimization algorithm: in the control strategy of the active filter, a dynamic optimization weight factor is introduced, enabling the filter to give priority to processing the harmonics with the greatest influence and realizing adaptive harmonic governance, improving the governance effect compared to fixed-parameter compensation.

[0049] Example 3, referring to Figure 2 , which is an embodiment of the present invention, provides a distribution network harmonic governance and heat loss evaluation system, including a harmonic analysis module, a cable temperature prediction module, and a governance optimization module.

[0050] Among them, the harmonic analysis module is used to collect distribution network signals, extract harmonic characteristics, and calculate the harmonic contribution degrees of each load based on harmonic power flow; the cable temperature prediction module is used to calculate the additional heat loss of the cable caused by harmonic current and predict the cable temperature based on the transient heat conduction equation; the governance optimization module is used to dynamically adjust the parameters of the harmonic compensation device and optimize the load scheduling according to the harmonic governance and heat loss evaluation results.

[0051] If a function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or a part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods of the various embodiments of the present invention. The aforementioned storage medium includes: various media that can store program codes, such as USB flash drives, mobile hard disks, read-only memories (ROMs, Read-Only Memories), random access memories (RAMs, Random Access Memories), magnetic disks, or optical discs.

[0052] The logic and / or steps represented in the flowchart or described in other ways herein, for example, can be considered as a definite sequence list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by an instruction execution system, apparatus, or device (such as a computer-based system, a system including a processor, or other systems that can fetch instructions from the instruction execution system, apparatus, or device and execute the instructions), or in combination with these instruction execution systems, apparatus, or devices. For the purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transmit a program for use by or in combination with an instruction execution system, apparatus, or device.

[0053] More specific examples (non-exhaustive list) of computer-readable media include the following: electrical connection parts with one or more wirings (electronic devices), portable computer disk cartridges (magnetic devices), random access memories (RAMs), read-only memories (ROMs), erasable programmable read-only memories (EPROMs or flash memories), fiber optic devices, and portable compact disc read-only memories (CDROMs). Additionally, a computer-readable medium can even be paper or other suitable media on which a program can be printed, because the program can be obtained electronically, for example, by optically scanning the paper or other media, then editing, interpreting, or otherwise processing it as appropriate, and then storing it in a computer memory.

[0054] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, any one or a combination of the following techniques well known in the art can be used: discrete logic circuits having logic gate circuits for implementing logical functions on data signals, application specific integrated circuits having appropriate combinational logic gate circuits, programmable gate arrays (PGAs), field programmable gate arrays (FPGAs), etc. It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

[0055] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A method for harmonic governance and heat loss assessment of a distribution network, characterized in that, Including: Collecting distribution network signals, extracting harmonic features, and calculating the harmonic contribution degree of each load based on the harmonic power flow; Calculating the additional heat loss of the cable caused by harmonic current, and predicting the cable temperature based on the transient heat conduction equation; According to the results of harmonic governance and heat loss assessment, dynamically adjusting the parameters of the harmonic compensation device and optimizing the load dispatching.

2. The harmonic governance and thermal loss assessment method for a distribution network according to claim 1, wherein: The extracting of harmonic features includes deploying harmonic monitoring equipment at the distribution network nodes, collecting three-phase voltage and current signals in real time, with the sampling frequency meeting the Nyquist sampling theorem to capture each harmonic component; Performing spectral analysis on the collected signals using Fourier transform to obtain the amplitude and phase information of each harmonic component, and combining with short-time Fourier transform for time-frequency domain analysis to extract harmonic variation features, identify harmonic sources, and quantify harmonic intensity.

3. The harmonic governance and thermal loss assessment method for a distribution network according to claim 2, wherein: The calculating of the harmonic contribution degree of each load includes, based on the harmonic current characteristics of each load in the distribution network, measuring the voltage and current at each monitoring point respectively, extracting each harmonic component, establishing a harmonic current injection model for each load, and calculating the harmonic current injection amount of each load; Based on the frequency-dependent characteristics of the line impedance, establishing a power grid impedance model at different harmonic frequencies, combining with the harmonic current injection models of each load, calculating the harmonic power flow at different frequencies, and solving the harmonic voltage at each node based on the iterative method to calculate the harmonic voltage distortion contribution amount of each load at each harmonic frequency; Based on the harmonic current injection amount of each load and the harmonic voltage distortion situation at each node, calculating the contribution degree of each load to the total harmonic distortion rate of the distribution network, and constructing a load harmonic contribution degree matrix according to the relative influence relationship of different loads to quantify the impact of each load on the overall power quality.

4. The harmonic governance and thermal loss assessment method for a distribution network according to claim 3, wherein: The calculating of the additional heat loss of the cable caused by harmonic current includes conducting electromagnetic field effect analysis, calculating the additional loss caused by the eddy current effect based on the non-uniform distribution of harmonic current in the conductor, and proportionally correlating the additional loss with the square of the harmonic frequency to distinguish the additional loss from the fundamental wave loss; Based on the heat conduction characteristics of the cable, establishing an internal heat transfer model of the cable, calculating the heat transfer rate between different layer structures of the cable according to the thermal resistance characteristics of the conductor and the insulation layer, taking the heat generated by harmonic loss as the heat source term, and deducing the temperature rise situation of the cable in the actual operating environment to quantify the impact of harmonics on the heat loss of the cable.

5. The harmonic governance and thermal loss assessment method for a distribution network according to claim 4, characterized in that: The predicting of the cable temperature based on the transient heat conduction equation includes using the transient heat conduction equation to establish a cable temperature field model and calculating the temperature rise trend of the cable over time; Monitoring the cable temperature through fiber optic temperature sensors and infrared thermal imaging equipment, and predicting the cable temperature in combination with time series to identify overheating risks in advance and optimize the cable operation management.

6. The method for harmonic governance and thermal loss assessment of a distribution network according to claim 5, characterized in that: The dynamically adjusting of the harmonic compensation device parameters includes, according to the measured harmonic frequency components, analyzing the amplitude and phase of each harmonic current, and calculating the total harmonic distortion rate of the current distribution network. If it exceeds the set target value, further analyzing the contribution degree of each load to the harmonics to determine the main harmonic source; According to the characteristics of the main harmonic sources, select the corresponding compensation strategy, adjust the output frequency band of the active filter according to the grid impedance characteristics of each harmonic frequency band, so that the output frequency band covers the main harmonic components, and at the same time adjust the compensation parameters of the passive filter to optimize filtering; After adjusting the parameters of the compensation device, re-obtain the harmonic measurement data of the distribution network, and calculate the total harmonic distortion rate after adjustment. If the target value is still not reached, iteratively optimize and adjust the operating state of the compensation equipment until the harmonic level drops within the set range or reaches the adjustment limit of the compensation device; During the adjustment process of the harmonic compensation device, detect the change of the cable temperature. If the temperature rise exceeds the safety threshold, limit the operating range of the compensation equipment.

7. The method for harmonic governance and thermal loss assessment of a distribution network according to claim 6, characterized in that: The optimization of load scheduling includes determining the current load operating state according to the cable temperature prediction result, and calculating the influence range of high-order harmonics on the cable temperature rise; Compare the predicted value of the cable temperature rise with the safe operating threshold. In the case of exceeding the safe operating threshold, use discrete-time dynamic programming to optimize the load scheduling and reduce the instantaneous peak load.

8. A system adopting the distribution network harmonic governance and heat loss assessment method as described in any one of claims 1 to 7, characterized in that: It includes a harmonic analysis module, a cable temperature prediction module, and a governance optimization module; The harmonic analysis module is used to collect the distribution network signal, extract the harmonic characteristics, and calculate the harmonic contribution degree of each load based on the harmonic power flow; The cable temperature prediction module is used to calculate the additional heat loss of the cable caused by the harmonic current, and predict the cable temperature based on the transient heat conduction equation; The governance optimization module is used to dynamically adjust the parameters of the harmonic compensation device and optimize the load scheduling according to the harmonic governance and heat loss evaluation results.

9. A computer device, comprising a memory and a processor, the memory storing a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the distribution network harmonic governance and heat loss evaluation method described in any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the distribution network harmonic governance and heat loss evaluation method described in any one of claims 1 to 7.

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